Chikungunya virus emerges as bigger threat to people in north India

Spread by the Aedes egypti mosquito, chikungunya will hit people in the north harder over the next few years, say experts. Data from last year shows out of 64,000-odd chikungunya cases from across the country, only about 18,000 were reported from the south.

Municipal workers fumigate a park in a bid to kill off mosquitoes in Bengaluru. Over 18,700 cases of dengue have been reported in India this year.(AFP)

Chikungunya, a mosquito-borne disease that causes debilitating joint pain, has emerged as a bigger threat than dengue for people living in north India than those in southern states that have had their share of outbreaks over the past decades.

The reason is simple: people in north India don’t have much immunity against this viral infection that rarely kills but causes severe pain that can last for years after recovery.

Spread by the Aedes egypti mosquito that also causes dengue, chikungunya will hit people in the north harder over the next few years till the population develop immunity against the virus, say experts. Government data from last year shows out of 64,000-odd chikungunya cases reported from across the country, only about 18,000 were reported from the states down south.

“Once you get exposed to the infection, you develop immunity for life, and people down south have mostly got immunity against chikungunya,” says Dr P Jambulingam, director, vector control research centre (VCRC) in Puducherry.

“However, in places where earlier the disease wasn’t common, now we see higher number of infections as people travel and aedes mosquitoes that act as carriers have also spread to all places. It will be some time before the numbers start coming down elsewhere.”

Killer or not— the debate

While government data shows more than 60,000 cases in one of the worst chikungunya outbreaks in the country in 2016, there was no death reported. The jury is still out on whether deaths among chikungunya positive people can be attributed to the viral infection or not.

“We have no evidence to prove that chikungunya has killed people in India. Chikungunya positive people who have died, have died due to co-morbid conditions,” says Dr AC Dhariwal, former head of the National Vector Borne Disease Control Programme (NVBDCP).

New Delhi’s Hindu Rao Hospital had said that four people who died while undergoing treatment at the hospital last year were chikungunya positive, of which two deaths could be attributed to the viral infection as they did not suffer from any underlying medical conditions.

Pika, 4, was admitted to the hospital early morning on September 17 and passed away five days later. The cause of death was viral meningoencephalitis, swelling and inflammation of the brain and its membrane.

Isha, 22, died of a cardiac arrest at the hospital on September 1. “…the girl did not have any pre-existing conditions, but developed myocarditis (inflammation of the heart muscle) and died of a cardiac arrest,” the hospital authorities had told HT. After hospitals started reporting deaths, government constituted an expert committee to analyse the deaths.

“The experts reached the conclusion that none of the deaths were due to the chinkungunya virus directly. There are some viral infections such as zika, scabies, or mild influenza that don’t kill. Un- like in dengue, where vascular permeability increases, leading to blood leaking, low blood pressure affecting the heart, chikungunya is not known to lead to any such complications,” said Dr Dhariwal.

What India lacks is a comprehensive study. “There needs to be more research in the area to be able to say anything conclusively,” says Dr Soumya Swaminathan, director general of the Indian Council of Medical Research (ICMR).

A national-level survey is on to study dengue prevalence in the country, which is lead by one of the ICMR institutes — the National Institute of Epidemiology in Chennai, Tamil Nadu. “We will be using the national prevalence study on dengue to gather relevant information on chikungunya also. It will help in knowing the disease burden in India and the percentage of people with anti-bodies in different states,” says Dr Swaminathan.

She is hoping that in a year’s time, India should be able to generate relevant data, and concrete information about the disease pattern.

Debilitating illness

People who are diagnosed with the disease suffer debilitating pain in their bones and joints, and could take many months to recover fully. The viral attack causes inflammation of muscle tissue around the main joints such as wrists, knee and elbows but why the extent of pain and why it stays for so long is unclear, say experts.

“There are not enough studies but the pain and long time to heal is mostly attributed to immunological response of the body to the process of inflammation. Your immune system attacks muscle tissue which leads to excruciating pain and difficulty in moving and doing chores that involve the joints,” says Dr Shah Alam, professor, orthopaedic department, All India Institute of Medical Sciences, Delhi.

Medicines and vaccines

There is no treatment currently prescribed for chikungunya -- people are given symptomatic treatment. The efforts are on to develop a vaccine and test potential medicines to treat the disease.

The Pune-based National Institute of Virology (NIV), which functions under ICMR, and Sun Pharma have signed a pact to test the company’s new medicines to combat dengue, chikungunya and zika. As part of the agreement, Sun Pharmaceutical Industries Ltd will provide drug molecules to NIV for testing against these three mosquito-borne infections.

“Unfortunately, no effective antivirals and vaccines are available for these infections yet. Our agreement with Sun Pharma aims to find a solution to these unmet needs,” said Devendra Mourya, NIV Director, while signing the pact.

Hyderabad-based Bharat Biotech has also entered human clinical trials for its chikungunya vaccine. The indigenously developed chikungunya vaccine—CHIKV— has entered the phase 1 trial to evaluate the vaccine’s safety, tolerability and immunogenicity.

There were some hiccups regarding the recruitment of volunteers for trials.

“There were some issues as the recruitment of volunteers was a bit slow. They wanted the number of sites to be increased, which is under consideration,” said Dr Swaminathan.

However, it could still be years before the vaccine finally is ready for use.

Breeding control

Since chikungunya is a disease that spreads through mosquitoes, preventing mosquito-breeding is the ultimate key.

Experts mainly talk of three ways that can be effective in controlling mosquito breeding— source reduction method, use of larvicide and biological control.

Source reduction method is when water is not allowed to get stored for more than a week, as disease-causing mosquitoes are capable of laying eggs even in 10ml water, which is a capful of water. Use of larvicides is helpful where it is not possible to remove stored water.

Anti-larval such as temephos can be used once a week at a dose of 1 parts per million, and pyrethrum extract can also be sprayed in rooms to kill the adult mosquitoes hiding in the house. The other option is biological control, using larvivorous fish— gambusia and guppy, in water tanks and other water sources to control breeding.

During a high-level review meeting earlier this month on preparedness for prevention and control of vector-borne diseases, Union health minister JP Nadda asked the states for mounting aggressive awareness campaigns to control mosquito breeding. “The government is doing its bit and people will have to do their by ensuring breeding control at their homes and surrounding areas,” he said.